RF switches are used in a variety of RF circuits to implement various functions. For instance, an RF system using different signaling methods over different frequencies may be implemented by using a network of antenna switches to select from between different types of RF front-end circuits. One example of such a circuit is a multi-standard cellular telephone that can make calls using different standards such as code division multiple access (CDMA) or Global System for Mobile Communications (GSM). By using an RF switch, an RF front end circuit optimized for CDMA communication may be used for CDMA calls, while an RF front end circuit optimized for GSM communication may be used for GSM calls. In addition, RF switches may be used to implement adjustable matching networks for antennas and power amplifiers, and to provide adjusting tuning for high frequency filters by switching in and out and/or bypassing passive matching and tuning elements.
As RF components are becoming more integrated in fine geometry integrated circuit processes, there are a number of technical challenges with respect to fabricating RF switches that have good high frequency performance. One such challenge is handling large voltage swings that may occur during the course of a signal transmission. In some cases, these voltage swings may exceed the breakdown voltages of the particular semiconductor process technology being used. One way in which this challenge is addressed is by stacking multiple devices and/or by using physically larger devices that may better withstand higher voltages. Another challenge to integrating RF switches involves managing the parasitic environment of the RF switch itself, as large devices used to withstand higher voltages may be prone to higher parasitic capacitances that may attenuate and/or degrade an RF signal. Examples of signal degradation include signal distortion caused by variations in bias voltage levels and parasitic capacitance over large signal swings.